DESCRIPTION (adapted from the Abstract): In this AIDS-FIRCA application the Principal Investigator proposes a United States-Peruvian collaboration to study human T-cell lymphotrophic virus type 1 (HTLV-I) infection among female sex workers (FSW's). HTLV-1 is a retrovirus which can cause tropical spastic paraparesis/HTLV-1 associated myelopathy (TSP/HAM). The natural history of sexually transmitted HTLV-1 infection in adults is largely unknown. The major goal of the proposed study is to characterize the neurological manifestations of HTLV-1 infection in FSW's in Peru. A secondary goal is to study risk factors for acquisition of HTLV-1 in FSW's. In a cross-sectional study, the Investigator and his associates will characterize neurologic abnormalities in (a) a cohort of 170 previously identified FSW's who are seropositive for HTLV-1, and 170 age-matched FSW's who are seronegative, and (b) a group of 50 patients with TSP/HAM. Neurologic evaluations of FSW will be performed blinded to HTLV-1 status and will include a simple screening performed by a trained non-physician, a standardized neurologic examination performed by a neurologist, and a quantitative spasticity assessment (QSA) of the lower limbs using a device developed at the University of Washington. The aims of the project is to (1) assess whether neurologic abnormalities in FSW's are more common among those seropositive for HTLV-1 than in those seronegative and (2) to identify prognostic factors among HTLV-1 positive patients that are associated with an increased risk of developing neurologic abnormalities. The researchers will follow, in a longitudinal study, all 340 of the FSW's from the cross-sectional study conducting neurologic evaluations every three months. The Investigator hypothesizes that (1) HTLV-1 seropositive FSW's will develop neurologic signs and symptoms more frequently than seronegative FSW, (2) those who are HTLV-1 seropositive and are neurologically impaired at an earlier examination will deteriorate over time, (3) the researchers will be able to identify prognostic factors of increased risk of neurologic deterioration, and (4) the researchers will be able to identify etiologic risk factors associated with acquisition of HTLV-1 expecting that both ulcerative and non-ulcerative STD's increase the risk of seroconversion. The Investigator expects to confirm the findings of earlier cross-sectional studies that duration of work as a FSW increases the risk of acquisition and condom use decreases the risk; he expects, also, to extend these findings with the incident cases from the longitudinal study.